The present invention relates to a method for the preparation of a fructose-containing oligosaccharide or, more particularly, to an efficient and economical method for the preparation of a fructose-containing oligosaccharide by using an enzyme P having high activity for the transglycosidation reaction.
Along with the increasing desire of people for more healthy life in recent years, intensive investigations are now being undertaken for the synthesis of oligosaccharides and useful glycosides having physiological activity in various respects by using a glucosyl group- or fructosyl group-transferase. Coupling sugar, fructo-oligosaccharides, palatinose, .alpha.-glucosyl stebioside and the like are some of the examples of those having no responsibility for carious teeth and acting as a growth factor of bifidus bacteria and hitherto rendered to practical application.
Known transferases of fructosyl groups include the levan sucrase produced by Bacillus subtilis and .beta.-fructofuranosidase produced by the fungi such as Aspergillus niger, Penicillium oxalicum, Penicillium frequentans, Penicillium sp. K25 and the like. It is also known that xylsucrose and isomaltosyl fructoside synthesized by utilizing the activity of levan sucrase among them for transglycosidation are characteristically cariostatic and lactosucrose has an activity as a growth factor of bifidus bacteria so that these oligosaccharides have a potentiality for practical application in the future as a functional saccharide. Since the levan sucrase used in the production of these oligosaccharides is derived from sucrose, it is indispensable that the culture medium contains sucrose so that levan is unavoidably formed in the liquid culture medium resulting in an increased viscosity of the medium to cause a difficulty in handling of the medium. As is pointed out, in addition, this enzyme has problems in respects of the low productivity, poor heat resistance and so on. Further, the .beta.-fructofuranosidase produced by conventional fungi is an endoenzyme of the fungal body and is defective in the narrow receptor specificity.
The inventors have previously discovered a species of microorganism Arthrobacter sp. K-1 (FERM BP-3192) having a broad receptor specificity and capable of producing a .beta.-fructofuranosidase having a high activity for the transglycosidation as an exoenzyme and established a method for the preparation of the .beta.-fructofuranosidase by culturing the microorganisms as well as a method for the preparation of an aldosyl fructoside by utilizing the thus obtained enzyme. No reports have yet been submitted, however, relative to the preparation of a fructose-containing oligosaccharide by utilizing this .beta.-fructofuranosidase.